1. Field of the Invention
The present invention relates to internally illuminated signs and, more particularly, to internally illuminated emergency signs using light emitting diodes as light sources therein.
2. Related Art
In the illuminated sign industry, particularly the emergency sign industry, it is important to provide a relatively small illuminated sign which exhibits evenly illuminated indicia while using as little energy as possible. In keeping, it is desirable to internally illuminate the sign using an efficient light source.
Internally illuminated signs, particularly Exit signs, are known in the art. For example, U.S. Pat. No. 5,542,201 shows an internally illuminated sign having a unidirectional light emitting diode (LED) array as a light source. The sign of the '201 Patent includes a housing having a top, a bottom, two sides, a front and a back where the LED array is disposed along a side of the housing. In an attempt to meet the needs of the art, the sign of the '201 patent, utilizing the unidirectional LED array, requires a special reflector for diffusing and directing the unidirectional light from the array out the front of the sign.
There is also a disadvantage in mounting the LED array to the side wall of a housing in an internally illuminated sign. Indeed, when the LED array is positioned on a side wall of a housing (as in the '201 patent) the additional reflector plate must include a special upturned section to direct light from the source out the indicia of the sign. The upturned section of the reflector is required because the single LED array is unduly far from the opposite side of the housing which also requires light.
Accordingly, there is a need in the art for a simple, cost effective, power efficient, and internally illuminated sign which utilizes a low energy but high intensity light source, for example an LED array, yet also evenly illuminates the indicia of the sign.
Internally illuminated signs of the prior art utilize an opaque cover having cut out portions forming indicia therein (sometimes called a stencil) to permit light to escape from within the sign an attract the eye of a viewer. When LED arrays are used to illuminate the sign, diffusers (as opposed to "fibers" which are used with incandescent light sources) are placed over the cut out portions to more evenly distribute the light emitting from the sign and mitigate hot spots.
The diffusers are typically formed from a solid extruded piece of transparent acrylic material which has been coated on one or both sides with red paint. Unfortunately, the steps required in the painting process adds manufacturing costs to the final product and often does not result in maximized diffusion and/or minimized attenuation of light. Accordingly, there is a need in the art for an improved diffuser which maximizes diffusion of light, minimizes attenuation of light and reduces the manufacturing costs of the sign.
In some States (for example Colorado and California), government requirements mandate that the illuminated indicia of an Exit sign be green. Such requirements are becoming increasingly popular. Unfortunately, commercially viable, high intensity, green LEDs are typically unidirectional and, therefore, there is a need in the art for a cost effective, efficient, and internally illuminated exit sign having evenly illuminated green indicia.
Also of import in the emergency sign industry, particularly the exit sign industry, is that an exit sign provide emergency battery backup power while meeting or exceeding the Underwriter Laboratories (UL) 924 Standard. Unfortunately, signs of the prior art either do not provide battery backup power or do not do so most efficiently and most cost effectively. Accordingly, there is a need in the art for an improved internally illuminated sign which meets UL 924 while maintaining low manufacturing costs and efficient power handling.
Further, it is important in the emergency sign industry that a sign provide emergency incandescent lighting. Unfortunately, prior art signs do not employ incandescent lighting units which are integral with an emergency sign, for example, an Exit sign. Accordingly, there is a need in the art for an Exit sign which employs an integrally mounted incandescent lighting unit which provides directionally adjustable incandescent lighting in emergencies.
Still further, designers of emergency signs have searched for a commercially viable method of mounting emergency signs, which method provides a customer with options as to whether the sign is to be top mounted, bottom mounted or side mounted to a wall, ceiling or the like. Unfortunately, prior art emergency signs do not provide such a commercially viable method. Accordingly, there is a need in the art for a new method of mounting emergency signs, which method provides a customer with optional top, bottom or side mounting of the sign.